The present invention relates to a printhead and a printing apparatus using said printhead, and more particularly, to a printhead structured such that a plurality of printing elements arranged in a predetermined direction and a driving circuit for driving the printing elements are provided on one substrate, and that the printing elements are divisionally driven in unit of plural blocks, and to a printing apparatus using said printhead.
A printing apparatus, such as a printer which prints data, such as desired characters or images, on a sheet-type printing medium, such as paper or film, is widely used as a data output apparatus in a word processor, personal computer, facsimile apparatus or the like.
Various printing methods of a printer are known. Particularly, an inkjet printing method recently receives attention because of the following reasons: capability to perform printing without contacting a printing medium such as paper, ease of color printing, and quiet printing operation. With respect to a structure of the inkjet printing method, serial printing method is widely adopted in general because it is low cost and easy to downsize. Serial printing realizes printing by reciprocally scanning a printhead, which discharges ink in accordance with desired printing data, in the direction intersecting with the printing medium conveyance direction.
As an ink discharging method of the inkjet printing method, method utilizing heat energy is known. In this case, the printhead comprises electrothermal transducers, such as heating elements, in the portions connected to discharge orifices which discharge ink droplets. The heating elements are electrified for a few xcexc seconds to generate bubbles in the ink, and pressure of the bubbles causes to discharge ink droplets, thereby realizing printing.
In a printhead of this type, it is easy to arrange a large number of discharge orifices and heating elements at high density. Therefore, high-precision image printing can be realized.
Assuming if all the heating elements of the printhead are simultaneously driven, the instantaneous current value becomes high. As a result, a large capacity of power source is required. In view of this, normally time-divisional driving is performed to keep a low instantaneous current value. In the time-divisional driving, few tens or few hundreds of heating elements are divided into a plurality of blocks, and the blocks are driven at slightly different timings.
Furthermore, to drive a large number of heating elements, a driving circuit of the heating elements is incorporated in the substrate of the printhead, keeping the number of wirings between the printhead and printer""s main unit low. A silicon (Si) wafer is widely used as a material (element substrate) of the printhead substrate, which incorporates the heating elements and driving circuit.
Among various structures of a circuit manufactured in the substrate, typical structure is described below.
A printing apparatus main unit serially inputs printing data and encoded block data through one signal line. A printhead, receiving the inputted data, comprises a shift register for sequentially storing the signal one bit at a time; a latch for temporarily storing the data stored in the shift register; a decoder for decoding the block data stored in the latch; an AND gate for obtaining AND of the latched printing data, decoded block data, and signal specifying the driving timing; and a driving transistor for driving each heating element in accordance with an output of the AND gate.
Herein, a value obtained by dividing the number of all heating elements by the number of blocks is the number of heating elements, which can be driven simultaneously, thus is a number of bits of printing data. Either a bipolar transistor or a FET may be used as the driving transistor.
However, the conventional printhead having an above-described circuit structure has the following problems.
The number of AND gates and driving transistors provided in the printhead corresponds to the number of heating elements. Therefore, in order to input decoded block data to each of the AND gates, the number of signal lines as many as the number of blocks is necessary between the decoder and AND gates. When there are a large number of heating elements, the wiring area of the signal lines is enlarged, making it difficult to downsize a semiconductor chip.
As a result, this wiring area limits the number of semiconductor chips, manufactured from one sheet of semiconductor wafer in the manufacturing process of a semiconductor chip that is used as a printhead substrate. For this reason, lowering the manufacturing cost of a printhead substrate becomes difficult. As a result, cost reduction of a printhead using the substrate becomes difficult.
The present invention has been proposed to solve the conventional problems, and has as its object to provide a printhead which can realize cost reduction of a printhead by reducing the area of a printhead substrate.
Another object of the present invention is to provide a printing apparatus using a printhead which can realize cost reduction of a printhead by reducing the area of a printhead substrate.
According to the present invention, above object is attained by a printhead structured such that a plurality of printing elements arranged in a predetermined direction and a driving circuit driving the printing elements are provided on one substrate, and that the printing elements are divisionally driven in unit of plural blocks, comprising: an input terminal serially inputting printing data corresponding to each printing element and encoded block data designating a block to be driven; a shift register sequentially shifting and storing one bit at a time the data serially inputted from the input terminal; a latch temporarily storing the data stored in the shift register; a decoder decoding the encoded block data among the data stored in the latch; and an AND circuit performing AND operation of the printing data outputted from the latch, an output of the decoder, and a driving signal designating driving timing of the driving circuit, wherein the decoder outputs a signal in which the encoded block data is partially decoded, and the AND circuit determines a block to be driven based on the partially decoded signal.
According to the present invention, above another object is attained by a printing apparatus utilizing a printhead structured such that a plurality of printing elements arranged in a predetermined direction and a driving circuit driving the printing elements are provided on one substrate, and that the printing elements are divisionally driven in unit of plural blocks, the printhead comprising: an input terminal serially inputting printing data corresponding to each printing element and encoded block data designating a block to be driven; a shift register sequentially shifting and storing one bit at a time the data serially inputted from the input terminal; a latch temporarily storing the data stored in the shift register; a decoder decoding the encoded block data among the data stored in the latch; and an AND circuit performing AND operation of the printing data outputted from the latch, an output of the decoder, and a driving signal designating driving timing of the driving circuit, wherein the decoder outputs a signal in which the encoded block data is partially decoded, and the AND circuit determines a block to be driven based on the partially decoded signal.
In other words, according to the printhead proposed by the present invention, a plurality of printing elements arranged in a predetermined direction and a driving circuit driving the printing elements are provided on one substrate. The printing elements are structured so as to be divisionally driven in unit of plural blocks. The printhead includes: an input terminal, to which printing data corresponding to each printing element and encoded block data designating a block to be driven are inputted; a shift register which sequentially shifts and stores one bit at a time the data serially inputted from the input terminal; a latch which temporarily stores the data stored in the shift register; a decoder which decodes the encoded block data among the data stored in the latch; and an AND circuit which performs AND operation of the printing data outputted from the latch, an output from the decoder, and a driving signal designating driving timing of the driving circuit. The printhead is constructed such that the decoder outputs a signal where the encoded block data is partially decoded, and that the AND circuit determines a block to be driven based on the partially decoded signal.
By virtue of the above construction, the number of signal lines outputted from the decoder is reduced, thereby enabling to reduce the area necessary for wiring the signal lines.
Accordingly, an yield of semiconductor chips manufactured from a piece of semiconductor wafer increases. Thus, it is possible to realize cost reduction of a printhead.
Furthermore, since the area necessary for wiring the signal lines is reduced, the wiring length of the circuit can be reduced. Therefore, radiant noise can be suppressed.
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.